Modern cellular base stations are separated into two units, a baseband unit and a remote radio head. The baseband unit, or baseband system, is located on the ground, often proximate to a tower. The baseband unit modulates and demodulates digital data. Thus, for example, the baseband unit includes with a modulator and demodulator.
The remote radio head coupled to, and mounted proximate to, one or more antennas on a tower. The remote radio head down converts and up converts the digital data to radio frequencies and amplifies received and transmitted radio frequency signals. This respectively enhances reception sensitivity and broadcast power of the cellular base stations. Thus, for example, the remote radio head includes an upconverter, a down converter, a low noise amplifier, and a power amplifier.
However, the use of a remote radio head requires that power be supplied to the remote radio head, on the tower, through a power cable. However, as disclosed in U.S. Pat. No. 9,448,576, because the length of the power cable can be hundreds of feet and the current drawn by the remote radio head can be, e.g., about 20 Amperes at a voltage level of about fifty volts, the power loss due to the power cable can be significant. U.S. Pat. No. 9,448,576 is incorporated by reference herein as if set forth in its entirety.
Power loss attributable to the power cable is problematic, if the cellular base station needs to operate on backup battery power in the event of a power blackout. The power dissipated by the power cable can be sufficiently large to undesirably reduce the operating time of the cellular base station when powered by a battery backup system. An equally undesirable alternative, due to increased cost, would be to compensate for the loss by increasing the number of batteries in the battery backup system.
To reduce the power loss, the voltage provided to the power cable can be increased to proportionally reduce the current that must be provided to power the remote radio head. The reduction in current reduces power dissipation by the square of the current reduction, or voltage increase.
U.S. Pat. No. 9,448,576 describes increasing the voltage applied to the cable above the maximum power rated input supply voltage for a remote radio head, and then lowering that voltage, with a DC-to-DC converter mounted on the tower, to a level less than the maximum rated input supply voltage for the remote radio head.
In addition to enhancing the performance of the battery backup system, the reduced current reduces cellular base station power dissipation, or ohmic losses, during normal operation, thus reducing operating expenses incurred by a cellular service provider. Alternatively, the cellular service provider can decide to accept higher power loss by utilizing thinner wires in the power cable. In this case, the provider can reduce capital expenditures, e.g. copper conductor costs, while sacrificing operating expenses.
However, operating at higher DC voltages can create risks for humans and cellular base station equipment. Also, DC-to-DC converters voltage levels of relatively high power levels can generate high heat levels. Therefore, there is a need for a system that enhances safety. Further, there is a need for DC-to-DC voltage converter systems that can readily dissipate high heat levels. Further, there is a need for architectures for implementing cellular base station using higher voltages.